Bulking method

ABSTRACT

A process for crimping cellulose acetate/cellulose triacetate conjugate filaments by treatment with reagents which preferentially disrupt the molecular orientation and crystallinity of the cellulose acetate followed by reagent removal and drying under conditions of substrate relaxation.

United States Patent Office.

3,605,224 Patented Sept. 20, 1971 3,605,224 BULKING METHOD Jesse L.Riley, William John Robert, and Walter C.

Zybko, Charlotte, NC, assignors to Celanese Corporation, New York, N.Y.No Drawing. Filed July 28, 1969, Ser. No. 845,503 Int. Cl. D02g 1/00 US.Cl. 28-721 22 Claims ABSTRACT OF THE DISCLOSURE A process for crimpingcellulose acetate/ cellulose triacetate conjugate filaments by treatmentwith reagents which preferentially disrupt the molecular orientation andcrystallinity of the cellulose acetate followed by reagent removal anddrying under conditions of substrate relaxation.

BACKGROUND OF THE INVENTION The present invention relates to a methodfor bulking conjugate filaments and/ or textile articles of manufactureproduced therefrom. More particularly, this invention relates to aprocess for spontaneously or latently developing bulk in conjugatefilaments and yarns composed of coextensive segments of celluloseacetate and cellulose triacetate.

Methods for producing multicomponent or conjugate filaments are wellknown inv the art. In US. Pat. 3,039,173, for example, there isdescribed a method involving spinning together two or more cellulosicderivatives, at least one of which is fiber-forming, in such a way thatthe derivatives are not appreciably blended together but rather formover the cross section of the single composite filament two or moredistinct zones which extend where desired throughout the entire lengthof the filament, whereby only one or, alternatively, part of or all ofthe components form the surface of the single composite filament. Theextrusion may be such that the components are localized and held in aside-by-side arrangement in which both components form part of thecomposite, or the extrusion may be such that one component forms a coreand the other a sheath to form a sheath-core composite. In this latterinstance, only the sheath contributes to the surface of the composite.See also US. Pat. 3,209,402, which describes method and apparatussuitable for producing multicomponent filaments and yarns. The contentsof each of the foregoing patents are incorporated hereby by reference.Thus, the term multicomponent filaments as used herein refers tofilaments formed from two or more fiber-forming masses wherein distinctzones of each mass remain segregated in coextensive relationshipthroughout at least a significant portion of the fiber as opposed to thehomogeneity associated with fibers formed from a blend of two or morefiber-forming components. Multicomponent and conjugate are usedinterchangeably herein to describe such fibers.

Multicomponent filaments that have proven to be of considerableimportance commercially are those made up of cellulose triacetate andsecondary cellulose acetate. It has been found desirable in preparingsuch bicomponent filaments to utilize two separate dope streams, one ofcellulose triacetate and the other of secondary cellulose acetate(hereinafter referred to as cellulose acetate). These two dope streamsare brought together in surface to surface contact, e.g. as byside-by-side arrangement, sheath-core arrangement, or the like, and theresulting composite dope stream is caused to flow by laminar viscousflow to a jet or spinnerette. The composite dope stream is extrudedthrough the jet so as to form a multicomponent (in this instance abicomponent) filamentary material made up of cellulose triacetate andcellulose acetate.

Prior to the present invention, it has been necessary to treat eitherthe raw cellulose acetate/cellulose triacetate multicomponent fiber ortextile articles constructed therefrom, i.e. knitted and woven textilematerials, by a timeconsuming and costly process involvingsaponification of the secondary cellulose acetate to regeneratecellulose to develop adequate fiber crimp and product bulk therefrom incombination with the dimensional stability required in commerciallyacceptable fibers. Selective saponification of the cellulose acetatecomponent of the conjugate fiber, generally consisting of a mildalkaline treatment, that is, an alkaline treatment bath sufficientlydilute so as not to appreciably affect the triacetate portion of thefiber, along with required post-saponification process steps such asresin treatment for added dimensional stability through repeatedlaundering cycles, heat setting, and tumble drying, develops sufiicientcrimp in the individual conjugate filaments to give textile materialsconstructed therefrom adequate hand, bulk, stability, and strength.Obviously, the employment of the conventional saponification treatmentis attendant with numerous disadvantages, most notable of which arecost, time, and required equipment.

An additional disadvantage associated with the saponification route fordeveloping bulk is the inherent conversion of cellulose acetate intoregenerated cellulose, the latter being highly undesirable in manyinstances as a conjugate fiber component. For instance, a celluloseacetate/cellulose triacetate multicomponent fiber would be preferable toa regenerated cellulose/ cellulose triacetate fiber because of thesuperior physical and chemical properties of cellulose acetate withrespect to certain endproduct manufacturing operations and resultingfabric uses. As examples of the above, others of which will be obviousto those of skill in the art, there may be mentioned the lower specificgravity of cellulose acetate, permitting a greater covering power andwarmth in a lighter weight fabric, solution dyeability, and excellentresistance to mildew.

Additionally, as compared to cellulose acetate, regenerated celluloseacetate is characterized by poor dyeing properties in certain respects,i.e. nonuniform pigmentation from disperse dye baths and general declinein dye substantivity, and lower productivity from an economic standpointdue to the approximately 17% weight loss resulting from saponification.Also, fabrics constructed from regenerated cellulose require resintreatments for dimensional stability with consequential fabric tenderingand yellowing.

Therefore, it is an object of the present invention to provide animproved process for bulking cellulose acetate/ cellulose triacetateconjugate fibers and textile materials constructed therefrom. Moreparticularly, it is an object of the present invention to provide arapid, inexpensive process for developing crimp in cellulose acetate/cellulose triacetate multicomponent fibers. A further object of theinvention is to provide a crimping process for conjugate fibers composedof cellulose acetate and cellulose triacetate which does not involveselective saponification of the celluloes acetate portion of the fiberto regenerated cellulose. Still another object of this invention is toprovide a bulking process for cellulose acetate/cellulose triacetatemulticomponent fibers which does not alter the chemical identity ofeither the cellulose acetate or triacetate component. An additionalobject of the invention is to provide a crimping process for celluloseacetate/ cellulose triacetate conjugate fibers which may be subsequentlyconstructed into fabrics retaining dimensional stability withoutrequiring a resin treatment. Other objects will appear obvious to thoseof skill in the art from the detailed description of the inventionhereinafter.

3 SUMMARY OF THE INVENTION In accordance with the present invention, ithas been found that treatment of conjugate yarns or filaments comprisingcellulose acetate/cellulose triacetate with a fluid capable ofdisrupting the molecular orientation and crystallinity of celluloseacetate without deleteriously affecting in a significant manner thedegree of crystallinity of said cellulose triacetate, followed byremoval of the fluid and drying of the substrate while in a relaxedstate, produces a differential shrinkage between the relativelyamorphous cellulose acetate and relatively crystalline triacetate, thelatter resisting shrinkage because of retention of its structuralintegrity, thereby producing crimped yarns or filaments. Preferably, thefluid treating agent is selected from the class of compounds whichfunction as sub-sol vents for cellulose acetate and, more particularly,is selected from the group consisting of water under conditions ofelevated temperature and superatmospheric pressure; and low molecularweight aliphatic and aromatic al cohols, carboxylic acids including theesters thereof, ethers and ketones including intramolecular condensationproducts such as lactones and aldehydes. These compounds will cause theconjugate yarns or filaments to develop adequate crimp not requiringselective saponification or other similar further bulking steps toenable the production of fabrics displaying excellent tactileproperties, loft, dimensional stability, strength, and other desiredcharacteristics. In preferred aspects of the invention, an aqueousformulation is employed for maximum development of shrinkagedifferential from a one step treatment, the water through its swellingeffect on the substrate further accentuating the shrinkage differential.Other acetate sub-solvents are known to those skilled in the art.

A variety of procedures are applicable for bulking the aforesaidconjugate filaments, which filaments are used to exemplify theinvention, involving contact with an appropriate chemical treating agentwhich upon fiber drying and/or subsequent thereto, i.e. followingconversion into fabric form, causes differential length change withrespect to the individual fiber-forming components of the celluloseacetate/cellulose triacetate conjugate fiber. The chemical agent candevelop dimensional change in either the cellulose acetate or triacetatecomponent or can affect both of said components, one to a lesser degreethan the other with the cellulose acetate when dried shrinking to agreater extent than the triacetate. The crimp effect occurs during asubsequent drying operation which activates a latent differentialshrinkability of the cellulose acetate vis-a-vis the cellulosetriacetate. Regardless of the type of length change, the resultant fiberis characterized by an area of cellulose acetate along the internalportion of the crimp, that is, the cellulose acetate shrinks to agreater degree than the cellulose triacetate fraction of the continuousfilament.

In one aspect of the invention, the conjugate filamentary material ispretreated to preferentially increase the degree of crystallization ofthe cellulose triacetate component or, alternatively, is pretreated toset up a high crystallization potential in the cellulose triacetatewhich is realized during subsequent fluid treatment. This effect may beaccomplished by treatment with cellulose triacetate swelling agents,which materials are well-known in the art, under conditions of exposurewhich may include a simultaneous or post-treatment stretch. In general,these materials do not produce a corresponding increase in degree ofcellulose acetate crystallinity. As a result, the shrinkability of thecellulose acetate fraction is not adversely affected during thesubsequent drying operation while the resistance to shrinking of thetriacetate is increased, because of the increased structural integrity,during processing. Following pretreatment, the multicomponent fiber iswashed and contacted before or after drying with the above-describedfluid treatment agent, i.e. cellulose acetate sub-solvent, with thedevelopment of an unusually high crimp level per unit relaxed length dueto My Ad the relatively stationary configuration of the cellulosetriacetate component from the crystallization thereof preventingshrinkage of the cellulose triacetate moiety to the degree possible inthe absence of the pretreatment. Where desired, latent bulkability isdeveloped by drying treated fibers under tension.

In another embodiment of the invention, which may also be considered asa preferred embodiment thereof, a textile substrate, i.e. fibers as wellas manufactured tex tile articles such as knitted, woven and nonwovenfabrics, may be simultaneously dyed and bulked with precise control ofdye uptake with respect to uniformity of shade by contact in a treatmentzone containing an appropriate dye and critical concentration ofchemical bulking agent. The accurate control of the concentration of thebulking agent enables it to function in two capacities during the dyeingprocedure, namely, as a dye levelling agent in addition to its functionas a crimp-developing compound. In this connection, it has been foundthat swollen fibers dye more rapidly.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aprocedure whereby conjugate filaments or yarns comprising celluloseacetate/ cellulose triacetate can be conveniently and inexpensivelycrimped during continuous operations not involving the disadvantages ofprior art selective saponification techniqucs.

It has now been found that certain fluids, particularly celluloseacetate sub-solvents, characterized by the ability to disorient andbreak down the weak crystallite ties of cellulose acetate withoutdisrupting, but in many instances improving, the crystallinity ofcellulose triacetate, differentially affect the dimensional stability ofthe individual components of cellulose acetate/cellulose triacetatemulticomponent fibers to such a degree that upon drying under relaxedconditions spontaneous crimping of the fibrous material occurs. Thetreating agents can preferentially operate on one of the yarncomponents, i.e. the acetate or differentially affect both the acetateand triacetate. Preferably, the treating agent is also a triacetateswelling agent and it should be noted that swelling agents fortriacetate which are not species Within the above general descriptionare applicable although not preferred in some instances.

In one aspect of the invention the fluids, particularly liquids,employed in the practice of the invention are oxygen-containingcompounds. The oxygen-containing compounds suitable for treating theconjugate filamentary material are low molecular weight aliphatic andaromatic carboxylic acids and esters thereof, alcohols, ketones, ethers,aldehydes, and lactones. The particular compounds employed may containan aromatic moiety with the proviso that the chemical compound does notcontain more than 10 carbon atoms in its structure. Preferably, thebulking agent will contain from 2 to 7 carbon atoms and will becharacterized by a phenyl group or two-carbon aliphatic chain within itsstructural formula and will be considered a sub-solvent for celluloseacetate. As representative compounds within the purview of the presentinvention, there may be mentioned water under elevated temperature andsuperatmospheric pressure conditions, acetic acid, amyl acetate, butylacetate, benzyl alcohol, phenol, butyrolactone, dioxane, acetone,nitromethane, formic acid, isopropyl alcohol, propionic acid, allylacetate, vinyl acetate, caprolactarn, urea, benzoic acid, sali cylicacid, diethylene glycol diacetate, glycerol diacetate, glyceroltriacetate, acetamide and ethylene glycol monomethyl ether. As is knownto those skilled in the art, as a general rule, organic sub-solventagents having hydroxyl functional groups may be employed as such whilethose deficient in hydroxyl functional groups are generally but notexclusively employed in a medium having such functional groups, ex, inaqueous solutions such as 2040% acetic or propionic acid in water byvolume, 3070% by weight aqueous solution of urea and the like, but itshould be noted that glycerol triacetate is operable in benzene solutionand vinyl acetate may be used undiluted. For optimum effect, theorganics are used in combination with water in one-step treatments atpreferred temperatures and concentrations with, in general,concentration of organic reagent decreasing as temperature is increased.

Many different treatment procedures may be employed as disclosedhereinafter as well as other contacting procedures, whether or not of acontinuous nature, which will be obvious to those of skill in the art.The essential requirements to be borne in mind are adequate contact timewith a treatment medium containing sufiicient concentration of chemicalagent to differentially affect the dimensional stability of theconjugate fiber and subsequent drying in an unrestrained condition or atleast with tension reduced sufficiently to allow the degree of crimpdevelopment desired. Preferably, the substrate material is washed toremove excess treatment agent prior to drying. Generally, the water washis also of benefit in enhancing the crimp effect because of its swellingaction on the conjugate fiber, that is, a higher percent crimp per unitlength is developed where the fibrous substrate is treated with one ofthe aforesaid chemical agents followed by a separate water treatmentbecause of a cumulative preferential dimensional instability resultingtherefrom.

As stated hereinbefore, the chemical reagents employed as bulking agentsherein disrupt the molecular orientation and weak crystallite tire ofthe cellulose acetate component, without freeing individual molecules ofthe point of complete solvation, i.e. structural integrity is lessenedbut still present, thereby allowing the cellulose acetate to appreciablyshrink following bulking agent removal and drying. This type of fluidaction is designated herein as sub-solvent action and the compoundsuseable are therefore sub-solvents for cellulose acetate. Simultaneouslywith sub-solvent action on the acetate, the treatment formulation mustnot significantly disrupt the crystallinity of the triacetate.Surprisingly, it has been found that in many instances cellulose acetatesub-solvents not only do not lower the structural cohesiveness of thetriacetate but actually increase the crystallinity of the triacetatebecause the increased mobility of molecular segments permits the fullerrealization of the potential for crystallization of the triacetate. Theswelling action, by permitting segmental rotation and relaxation ofstored stresses, removes some of the restriction on crystallite growthand results in an improvement in triacetate crystallinity. Thetriacetate, because of its retention of a high degree of crystallinity,exhibits minimal if any shrinkage during the subsequent dryingoperation.

It is to be understood that the present invention is applicable totextile substrates of any type comprising cellulose acetate/cellulosetriacetate conjugate fibers or yarns including, but not limited thereto,staple fibers, spun yarns, continuous monoand multifilaments and textilefabrics made therefrom, i.e. by various methods of interlacing such asweaving, braiding, knitting, twisting and the like, as well as nonwovenfabricating techniques. The terms fiber, filament and the like, are usedinterchangeably throughout the specification.

Likewise the invention is equally applicable to other cellulose esterswherein the ester group contains up to 4 carbon atoms, i.e. cellulosepropionate, cellulose butyrate and mixed esters thereof such ascellulose acetate-butyrate, cellulose propionate-butyrate and the likeas long the components of the conjugate filament have a degree ofesterification difference of at least about -15 percent based on percenthydroxyl radicals esterified, generally with the triester having adegree of esterification of about 2.9 to 3.0 and the diester about 2.0to 2.6. At times, the inclusion of priopionate and higher ester groupsubstituents in the bicomponent i.e. cellulose acetate/cellulosepropionate, will yield sufficient differential shrinkability under thedisclosed process conditions.

Certain treatment procedures are of particular utility in the bulking ofcertain types of substrate materials such as fabrics while othertechniques will lend themselves more to the crimping of continuousfilaments during multistep processes which impart additional desiredproperties to the substrate during an integral process.

For example, in one method in accordance with the invention, acontinuous strand of material comprising cellulose acetate/cellulosetriacetate in co-extensive relationship is passed sequentially throughan aqueous treatment bath containing a chemical bulking agent asdisclosed which causes latent differential shrinkage of the conjugatefiber and a second bath of cold water wherein no significant shrinkageoccurs. Subsequently, the strand, which could be a spun yarn,monofilament, or one member of a multifilament, tow and the like, isdried, such as by single or multiple simultaneous passage through anelongated oven, under relaxed conditions to allow maximum crimpdevelopment. At times, if a crimp level below that obtainable under theabove conditions is desired, the strand can be dried under a tensionsuflicient to prevent the cellulose acetate from shrinking to the degreepossible under unrestrained operating conditions. However, unlessblocked by subsequent treatment, water washing and drying at a latertime will develop additional bulk due to a memory effect produced in thefiber. A latent crimp development is desired at times since the yarn isthereby in a straight configuration during the conversion operation,i.e. weaving.

One of the particular advantages of this invention is that it provides arapid procedure for producing bulky fabric materials. Many fabricfinishing operations involve treatment in baths of various formulationsfollowed by drying in unrestrained condition. In such instance, thechemical bulking agent can most often be added in sufficientconcentration directly to such baths eliminating the necessity ofadditional treating units, time, etc. Alternatively, the fabric may beimmersed in a separate bulking bath prior to dyeing. As an example ofthe former and obviously preferred procedures, the chemical treatingagent can be incorporated into a suitable dye bath during a simultaneousdyeing and bulking operation.

It is preferred that an inexpensive bath medium be em ployed. In mostinstances, the treating medium will be predominantly water. To assureadequate fiber swelling, it is desirable to employ a hydrophilictreating medium containing hydroxyl groups to disrupt internalhydrogenbonding of the secondary acetate.

As disclosed hereinbefore, one of the preferred embodiments of theinvention resides in a prebulk or two-step treatment involving apretreatment to preferentially affect in a positive manner thecrystallinity of the cellulose triacetate component. This can beaccomplished by contact with a first, preferably mild, cellulosetriacetate swelling agent. The multicomponent material is then treatedwith a bulking agent as disclosed, that is, a material as describedabove which imparts a different shrinkability potential to celluloseacetate and cellulose triacetate so as to preferentially shrink thecellulose acetate component upon drying.

It has been found that the sequential treatment imparts a greaterrelative degree of crimp in the conjugate fiber than would be expectedfrom a consideration of the activity produced by the separateapplication of each treatment agent on comparable material. Thissynergistic effect is particularly evident Where, as preferred, thefirst treatment agent is one which has a relatively low degree ofactivity on cellulose triacetate crystallinity. In fact, in the absenceof a concomitant stretch being imparted to the textile substrate, noincrease in triacetate crystallinity is observed in most instances bythe usual testing methods. Any increase in crimp development uponsolvent removal and drying would be negligible since the pretreatmentagent is preferably also a poor sub-solvent for cellulose acetate. It ispostulated that the initial swelling agent treatment allows triacetatemolecules to move freely into a more natural molecular alignmentconducive to subsequent crystallization upon latter solvent treatment;that is, a high crystallization potential is set up in the triacetateportion of the material which potential is realized upon subsequenttreatment. Additionally, the number of small crystallites in thetriacetate is increased. Where desired, for maximum effect, thesubstrate is axially stretched up to its elastic limit simultaneouslywith swelling agent treatment for molecular orientation along thelongitudinal fiber axis. As a result, further triacetate crystallizationis accomplished, increasing the degree of crimp developed followingsubsequent treatments as described. The simultaneous stretching of thecellulose acetate when this embodiment of the invention is employed alsoincreases the shrinkage potential thereof.

The pretreatment agent may be selected from two broad categories oftriacetate swelling agents. On the one hand, swelling agents forcellulose triacetate which produce a small increase in triacetatecrystallization, even in combination with fiber stretching, may be used.As examples of this former type of swelling agent, there may bementioned the lower monohydric alcohols containing 1-4 carbon atoms inthe molecule, ex. methanol, ethanol, n-propanol, n-butanol, and thelike. The other general classification would include triacetate swellingagents having, in certain concentrations and formulations, a sutficienteffect on acetate to allow their use as the sole bulking agents in otherembodiments of the invention. However, for good synergism, this secondgroup of reagents, Where used as the pretreatment crystallizationpotentiator, are preferably employed in concentration and/ orformulations which are not useable per se as sole treatment agents.Indeed, at times the identical swelling agent may be employed in bothsteps of the sequential process with a non preferred formulation beingemployed in the first phase and optimum parameters being employed in thefinal acetate sub-solvent treatment. As examples of this latter type ofagent, other examples of which are stated throughout the specificaion,there may be mentioned methyl acetate, ethyl acetate, methylenechloride, gamma-butyrolactone, phenol and the like. For many of thesereagents, optimum concentrations and/or formulations for use astriacetate swelling agents are disclosed herein and in the patent andliterature arts. Where such data is not known precisely, routineexperimentation capable of those of ordinary skill in the art willsuffice once the principles as described herein are known.

The preferred pretreatment agent, recommended for ease of handling aswell as accessability, is ethanol. Pure,

i.e. about 9599% ethanol, need not be employed, but an aqueous mixturecontaining at least about 60% by volume ethanol, preferably over 65% byvolume, and most preferably about 80% ethanol, will functionsatisfactorily. Ambient temperature conditions may be employed andpreferably the temperature of treatment will be about 20 C. althoughtemperatures within the range of about C. up to about the boiling pointof the mixture are applicable with reduction in concentration atelevated temperatures. Concommitant with such a pretreatment, thetextile substrate is desirably placed under tension to effectuate alongitudinal stretch of the conjugate filaments, usually up to about a20% increase in length and preferably about l5%. Although, as describedhereinbefore, fiber extension is not essential to achieve the enhancedpercent crimp obtainable through pretreatment where a reagent such asethanol is employed which preferentially crystallizes cellulosetriacetate during stretching, it is highly desirable to stretch theconjugate filament for the additional molecular alignment associatedwith the orientation process. Depending upon degree of activity andwater miscibility, effective concentrations of other pretreatment agentsmay not coincide with that of ethanol as disclosed above, and routineexperimentation within the skill of those knowledgeable in the art maybe neces- 8 sary to optimize processing conditions within the generalparameter stated herein.

Concentration of the primary treatment agent will depend upon a numberof interrelated factors, the most important being the particular bulkingreagent selected. In general, considering an aqueous treating bath withpercent being either weight/volume or volume/volume reagent/dispersionmedium, according to the physical state of the chemical compound,concentration may range from 0.1 to about 100, i.e. no treatment medium,but most often will range from about 0.5 to percent with optimumconcentrations for most reagents being in the range of about 1 to 25percent. Thus, a relatively low concentration of chemical compound isgenerally required with no appreciable benefit and in many instancesvery poor results being observed with the use of higher concentrations.

As disclosed hereinbefore, the dispersion medium is preferably of ahydrophilic nature containing hydroxyl functional groups. Most often,where employed the dispersion medium is selected from acetate swellingagents and acetate sub-solvents and where applicable will preferably bewater. Thus, a binary system is desirable consisting of an optimumconcentration of water-soluble or miscible reagent in combination withwater. Of course, ternary and the like systems wherein two or moreorganic solvents or subsolvent agents for acetate are dissolved in, forexample, an acetate swelling agent treatment medium, are operable. Inone aspect of the invention, an acetate solvent, e.g. acetone, is usedin combination with an acetate swelling agent, i.e. water, to yield asub-solvent mixture. Concerning selection and proportions, one of themost critical factors to be borne in mind is to avoid completedissolution of triacetate (or other substrate components). Thus,triacetate solvents are employed under conditions such that theyfunction only as sub-solvents, i.e. 100% methylene chloride ispreferably applied as a vapor for rapid dissipation.

Considering the cellulose acetate/cellulose triacetate multicomponentmaterial in greater detail, the conjugate fiber may be of any desiredcross-sectional configuration, i.e. sheathcore as well as side-by-sidetype, and preferably the components are in eccentric relationship.Assuming a bicomponent fiber, ratio by weight may range from about 2:11:2 with 1:1 being preferred.

Treatment temperature can fluctuate widely and where treatment baths areemployed will usually be within the range of about room temperature upto the boiling point of the bath. Temperatures within the range of about30 C. to 70 C. are usually adequate with a shorter residence time andlower concentration generally being associated with increasedtemperatures. Temperatures above the designated range can be employedwhere autoclaves and other similar devices are used during substratetreatment. Residence time is normally about /2 minute to minutes to becorrelated with bath concentration, bath temperature, type of substrate,degree of crimp desired and the like. No specific advantages other thanthe stated use of lower reagent concentrations are known from practicingthe invention at higher temperatures, under applied pressures (exceptwhere water is the sole treating agent) or for longer residence times.Water washing temperature can range from below room temperature up totemperatures which do not adversely affect the substrate, but the waterwash will generally be under ambient conditions. Immersion baths,spraying booths and similar washing arrangements may be employed. Thebulking agent should be substantially removed from the substratematerial to eliminate any residual swelling effect after crimpdevelopment. This could seriously impair yarn and fabric strength. Sincewater is readily evaporated during the drying operation, it is thepreferred washing or solvent removal medium. Of course, other washingagents, such as ethanol, may be employed. Also solvent removal may beaccomplished during drying without a previous wash where treating agentsof high vapor pressure are employed.

The drying cycle, being essential for adequate bulk development, shouldbe accurately controlled. It is recommended that temperatures fromambient to below about 195 C., preferably 140l60 C., be employed forplanar substrates to allow diiferentail shrinkage of the conjugatematerial. Thus, drying time and temperature should be regulated so thatthe particular substrate, and of course considering the gross amount ofmaterial being dried where tumble drying units are used, will not be toorapidly dried with only a small number of crimps being formed. Thesubstrate must either be in a relaxed state, that is, under conditionsallowing freedom to contract, or under reduced tension during drying. Ifconstrained, the conjugate fibers can not shrink to develop adequatebulk. For maximum crimp development, elevated temperatures are usuallyrequired.

The following examples illustrate the invention. It is, of course,understood that the invention is not to be limited to certain of thepreferred embodiments of the invention as exemplified by the examples.

EXAMPLE 1 This example concerns one of the preferred embodiments of theinvention wherein triacetate/acetate conjugate filaments are pretreatedprior to actual bulking. Upon immersion in the bath of the primary bulkdeveloping chemical treating agent, the cellulose acetate swellssomewhat and relaxes while the cellulose triacetate component swells butremains relatively intractable.

A multililament yarn having a 1.2 gram per denier tenacity and 20%elongation at the break, each filament being of about 5.5 denier andcomposed of 50/50 by weight cellulose acetate/ cellulose triacetate incoextensive side-by-side relationship, is immersed in an ethanol/watersolution 80/20 by volume at 20 C. and suflicient tension is applied toelongate the yarn approximately 20% based on initial length. The yarn isdried unrestrained at room temperature with minimal crimp developmentand samples thereof are immersed in phenol solutions of varyingconcentrations at 55 C. for minutes. Each sample of yarn is then dippedin a water wash bath for one minute at room temperature and finally airdried under relaxed conditions at 60 C.

Table 1 presents the results obtained.

TABLE 1 Sample: *Degree of bulk AUntreated None. BTreated with 1%%phenol Fair. B Treated with 1%% phenol Do. CTreated with 2 /2 phenolGood. C Treated with 2 /2 phenol Do.

*In all of the examples herein the bulk rating is determined by visibleexamination in combination with measure ments of length shrinkage andcrimp level by one skilled in the art with a fair rating beingcorrelateable to the minimum bulk level acceptable for commercialproducts. For end products requiring a high degree of texture, i.e. bulky knits such as sweaters, 13. good to excellent rating would -berequired in the yarn.

Further experimentation indicates that optimum process parameters forthe phenol treatment are from 1 to 60 minutes in a 1-3% by weightaqueous bath at Example 1 is repeated with the elimination of theethanol pretreatment. Bulk development following washing and drying issomewhat lower than that shown by Table l but still appreciable.

EXAMPLE 2 This example concerns treating the foregoing bicomponentfilaments with aqueous solutions of amyl acetate, butyl acetate, andbutyrolactone, by immersing the filaments in a bath thereof.

When amyl acetate or butyl acetate is to be employed, inasmuch as theyare each of rather limited solubility in water, it is preferred toemploy as the solvent an aqueousalcoholic mixture, or water plus someother appropriate co-solvent.

Suitable alcohols that may be employed include methanol, ethanol,propanol (desirably isopropanol), or any mixtures thereof. Theconcentration of the alcohol in the water desirably should be from about10 to 50% by volume. The concentration of the amyl and butyl acetate inthe foregoing alcohol-water mixture was advantageously from about 2 to20% by Weight. Of course, these particular co-solvents areadvantageously employed for a cumulative effect since they are withinthe scope of the invention.

When butyrolactone is utilized rather than amyl or butyl acetate, thealcohol is desirably not employed in combination with the water as thesolvent. The concentration of the butyrolactone in the water is fromabout 5 to 25% by weight.

The temperature of the treating bath should desirably be from about 20to C., a preferred range being from about 40 to 90 C., the mostpreferred range being from about 70 to 90 C.

The residence time of the conjugate filaments in the bath may again vary:within considerable limits, generally being form about 1 to 60 minutes.Of course, a residence time in excess of 60 minutes could be employedbut would serve no additional advantage. A more preferred time range isfrom about 2 to 20 minutes, the most preferred range being from about 2to 10 minutes.

Following the immersion of the conjugate filaments in the aqueous oraqueous-alcoholic treating solution, the filaments are removed andwashed with water. Advantageously, this washing is carried out first incold water and thereafter with boiling water. The washing is desirablycarried out for from about 1 to 10 minutes with water at from about 20to C. Of course, the filaments could be washed with a non-swellingorganic solvent and immediately dried with good bulk development.However, this example illustrates the preferred washing method. Theforegoing water wash serves to remove the acetate sub-solvent (amylacetate, butyl acetate, or butyrolactone). Moreover, it will be notedthat the water is itself something of a swelling agent for both thecellulose acetate and the triacetate. Of course, because of the presenceof more hydroxyl groups in the cellulose acetate, the water tends toexert a greater swelling action thereon than upon the cellulosetriacetate. This difierential swelling is further enhanced due to thefact that the triacetate has in a sense been stabilized by virtue of theprevious solvent treatment, making it all the more resistant to swellingby the water wash. Thus, water in the absence of pressure (see Example 5hereinafter) is not considered as useable alone as a bulking reagent butonly for its additive elfect in binary and the like formulations. Attimes it may be employed as a pretreatment agent.

The water wvash is followed by drying of the filaments under relaxedconditions, generally either in air or alternatively in a tumble dryer.The drying results in a differential shrinkage between the acetate andtriacetate, the former shrinking markedly more than the latter, so thatthe drying develops a marked crimping of the multicomponent filamentswith a corresponding bulking thereof. Such bulking, of course, greatlyimproves the covering ability of the filaments, improves the hand, andgenerally imparts the usual desirable qualities associated with bulking.

Fabric samples knitted from the described conjugate filaments aretreated in alcohol-water or water solution of varying concentration ofbutyrolactone and amyl acetate for 10 minutes at 85 C. and 3 minutes at50 C l l respectively, as tabulated in Table 2 followed by washing inwater at 20 C. for 5 minutes and/or washing in boiling 'water forminutes, and in every case tumble drying at 160 C. for minutes.

TABDE 2 Water Boiling Wash water Degree Sample Bulking agent (20 C washof bulk 2A. None 10 2O 5% butyrolactonc Yes Fair. 2]) ..do Yes Yes...Do.1 2E 10% butyrolactonc Yes Good 2F do Do. 2G 20% butyrolactone. Verygood. 21L do Excellent.

Methanol/watei 50/5 Fair. 15 O O. 5% amyl acetate in nr/w. Yes Good.

50/50. 2L do Yes Yes..." Do. 2M 10%[amyl acetate in m./w. Yes Very good.

50 50. 2N do Yes... Yes Excellent. 2

1 Also 3 minutes at 50 C.

Equally good results are obtained with butyl acetate. Of interest is thebulk developed by the methanol/water solvent treatment illustratinganother composition com- 25 ing within the scope of the invention butmore desirably employed only as a pretreatment agent.

EXAMPLE 3 This example illustrates another of the preferred embodimentsof the invention wherein simultaneous dyeing and bulking of fabric areaccomplished.

Two-inch squares of a double knit fabric knitted from 180 denier 50/50by weight acetate (acetyl value of 55)/ triacetate conjugate filamentyarn as described are immersed in dioxane/water solutions of varyingdioxane concentration at about 25 C. for about 10 minutes. Also includedin the bulking chemical bath is 3% (w/w.) of Blue BGLF acetate dispersedye (available from Eastman Chemical Corp. of Kingsport, Tennessee)which produces visible dye streaks of different shades if the acetatesubstrate does not take up a uniform level of dye across its surface.This dye is the most senitive known for developing streaks because ofuneven dyeing. The squares are then washed in cold water (20 C.) for 10minutes and tumble dried at 160 C. The results are tabulated below inTable 3.

EXAM PLE 4 Example 3 is repeated in the absence of the dye with aceticacid/water solutions of varying acetic acid concentration. Optimumbulking is observed at the 35-40% acetic acid level.

EXAMPLE 5 Fabric samples as in Example 3 are immersed in a water bath at25 C. for 15 minutes, after which the samples are steam autoclaved for30 minutes at 15 p.s.i.g. The double knit fabric exhibits a bulk ratingof good. Increasing the pressure by 5 p.s.i.g. increments up to p.s.i.g.does not improve the degree of bulk developed.

EXAMPLE 6 Example 3 is repeated with varying levels of benzyl alcohol inwater at l25 C. With concentrations of 2 to 2 /2% of benzyl alcohol,good bulking accompanied by level dyeing is observed.

1 2 EXAMPLE 7 This example illustrates the use of the teachings hereinto produce latent bulkable fabrics.

A 60 denier, l7 filament multifilament conjugate yarn comprisingbilateral filaments of 50/50 bright acetate/ bright triacetate asdescribed is immersed in an aqueous solution of 40% volume/volume aceticacid/water at 25 C. under slack conditions, that is, without tension.The yarn is then wound loosely arounnd a metal frame after which it isimmersed in a water bath having a temperature of about 25 C. for aperiod of about five minutes. The yarn is observed to become taut on themetal frame. The metal frame and yarn are taken from the water bath andthe yarn is allowed to dry in air at room temperature. After drying, theyarn is cut off the frame and observed to be straight and to have shrunkl to l /2%.

A fabric knitted from the above yarn, although displaying no bulk orother texture, becomes highly bulked due to latent crimping of the yarnwhen immersed in cold water (25 C.) for one minute followed by drying atC. in a tumble dryer.

Obviously, this example can be the basis of a continuous operation forproviding latently texturable yarn to the trade, which yarn, uponwashing and drying, will latently bulk. Thus, in accordance with thisaspect of the present invention, conjugate filaments may be extruded toform a conjugate filament yarn. The yarn is then supplied in a pluralityof packages on a creel and is then beamed on a tricot beam. Between thecreel and the beam the yarn ends are passed through a vessel containingthe solvent treating material, e.g. 40% acetic acid/ water(volume/volume) followed by washing and drying under a tension of sayone sixtieth of a gram per denier. The yarn is then taken up on the beamin a straight manner, that is, without having been bulked. The yarn fromthe tricot beam is then knitted into the desired fabric or garment. Uponwetting, as in the scour operation, followed by drying, crimps areformed and the yarn becomes bulky, thereby producing an end producthaving a decreased air permeability, lofty hand, and the various otherdesirable attributes associated with bulky yarns.

Various modifications may be made within the scope of the inventionwhich will appear obvious to those of skill in the art. For example,conjugate filament material of cellulose acetate/triacetate bulked asdescribed herein may be selectively saponified in accordance with priorart techniques to produce a product which has a better dimensionalstability than comparable saponified yarns which have not beenpretreated in accordance with the invention. Further, the presentinvention is equally applicable to conjugate or more preciselycombination yarns per se, as opposed to conjugate filaments, composed ofcoextensive filamentary components which are differentially shrinkableor elongatable under the conditions of treatment, i.e. crepe fabrics maybe prepared from tricot fabrics knitted from a metier plied yarn ofnylon/acetate or nylon/acetate/triacetate conjugate filaments whentreated, for example, with acetic acid/water solution according to theexamples hereinbefore because of the differential shrinkage developedbetween the nylon and acetate or conjugate filament. At times it may bedesirable to preshrink one of the yarn components if the degree ofshrinkability therebetween is less than about 5% under treatmentconditions, i.e. a yarn composed of preshrunken nylon/acetate-triacetateconjugate filament may be bulked by treatment with benzyl alcohol inaccordance with the invention. In other modifications of the invention,one of the components of the cellulose acetate/ cellulose triacetate,conjugate substrate i.e. the acetate, may be blended with a thirdpolymeric fiber-forming material miscible therewith such as an acrylicpolymer to affect fiber strength and other properties as desired. Ofcourse, the conjugate components may contain normally acceptablemodifiers, i.e. TiO filler, be preferentially dyed and the like or thetreating agent may be applied intermittently in random or predeterminedfash ion for novelty effects. Further modifications, such asconstructing a. fabric from bulkable and non-bulkable fibers accordingto a preselected pattern for latent bulk development will appear obviousto those of skill in the art.

What we claim is:

1. A process for developing crimp in a cellulose acetate/cellulosetriacetate conjugate yarn or conjugate filament substrate which includesthe steps of:

(l) contacting said substrate with a fluid capable of disrupting themolecular orientation and crystallinity of said cellulose acetatewithout deleteriously affecting in a significant manner the degree ofcrystallinity of said cellulose triacetate, said fluid being selectedfrom the group consisting of water and low molecular Weight aliphaticand aromatic alcohols, carboxylic acids, carboxylic acid esters, ethers,ketones, lactones and aldehydes, said water being under conditions ofelevated temperature and atmospheric pressure, and mixtures thereof;

(2) substantially removing said fluid from said substrate; and

(3) drying said substrate under conditions of relaxation todifferentially shrink said cellulose acetate and said cellulosetriacetate, thereby crimping said cellulose acetate, cellulosetriacetate yarn or filament.

2. The process of claim 1 wherein said fluid is selected from the groupconsisting of dioxane, acetic acid, acetone, benzyl alcohol, phenol,amyl acetate, butyl acetate and butyrolactone.

3. The process of claim 1 wherein said substrate is a textile fabric.

4. The process of claim 1 wherein said fluid is a compound containing upto about 10 carbon atoms.

5. The process of claim 1 wherein said fluid is a subsolvent forcellulose acetate.

6. A process for developing crimp in a cellulose acetate/cellulosetriacetate conjugate yarn or conjugate filament substrate whichcomprises increasing the degree of crystallinity of said cellulosetriacetate by treating said substrate with a swelling agent forcellulose triacetate and then treating said substrate with the processof claim 5.

7. The process of claim 6 wherein said substrate is stretched along thelongitudinal axis of the yarn or fi1ament during said swelling agenttreatment.

8. The process of claim 7 wherein said yarn or filament is stretchedbelow its elastic limit.

9. The process of claim 6 wherein said swelling agent is selected fromthe class consisting of low molecular weight aliphatic monohydricalcohols.

10. The process of claim 9 wherein said alcohol is ethanol.

11. The process of claim wherein steps (2) and (3) thereof aresimultaneously accomplished.

12. The process of claim 5 wherein said conjugate filament is onecoextensive filamentary component of a conjugate yarn, at least a secondcomponent of said 14 conjugate yarn and said conjugate filament having adifferential shrinkability of at least about 5 percent when treated bythe process of claim 2.

13. The process of claim 5 wherein step (2) is accomplished by washingsaid substrate with water.

14. The process of claim 5 wherein said sub-solvent is a mixture of twoor more cellulose acetate sub-solvents.

15. The process of claim 5 wherein said sub-solvent is applied in anaqueous formulation.

16. The process of claim 5 wherein said substrate is also contacted witha dye during step (1).

17. The process of claim 16 wherein said sub-solvent is employed in aconcentration to maintain level dye pick-up by said substrate.

18. The process of claim 17 wherein said sub-solvent is selected fromthe class consisting of benzyl alcohol and dioxane.

19. A process for developing crimp in a cellulose acetate/cellulosetriacetate conjugate yarn or conjugate filament substrate whichcomprises preferentially setting up a high crystallization potential insaid cellulose triacetate and then treating said substrate with theprocess of claim 2.

20. A process for producing latently bulkable celluloseacetate/cellulose triacetate conjugate yarn or conjugate filament whichcomprises (1) contacting said yarn or filament with a fluid capable ofdisrupting the molecular orientation and crystallinity of said celluloseacetate without deleteriously affecting in a significant manner thedegree of crystallinity of said cellulose triacetate; (2) substantiallyremoving said fluid from said yarn or filament; and (3) drying saidsubstrate under conditions of constraint to prevent significantshrinkage of said yarn or filament to produce essentially straight yarnor filament suitable for textile conversion operations.

21. The process of claim 20 wherein said fluid is a subsolvent forcellulose acetate.

22. A process for producing bulky textile fabric materials constructedof cellulose acetate/cellulose triacetate conjugate yarns or conjugatefilaments treated in accordance with the process of claim 21 whichcomprises constructing said yarns or filaments into a textile fabricmaterial; wetting said fabric material and drying said fabric materialunder conditions of relaxation sufficient to differentially shrink saidcellulose acetate and said cellulose triacetate, thereby crimping saidcellulose acetate/ cellulose triacetate yarns or filaments to produce abulky fabric material.

References Cited UNITED STATES PATENTS 2,375,864 5/1945 Morgan 8--l312,408,381 10/1946 Dodge 8l31 3,039,173 6/1962 Mehler et al. 161173X3,057,038 10/1962 Soehngen 161173 3,128,148 4/1964 Moore et al. 8131LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R.

PO-T w UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3, 05,224 Dated September 20, 1971 fl flesse L. Riley, William JohnRoberts & Walter C. Zybko It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 3, "Robert" should read "Roberts" Column 4, line 58, theword "atom" should be inserted prior to the word "aliphatic" Column 9,line 7, the word "differentail" should be "differential" Column 10, line30, the word "form" should read "from" Column 10, line 51, the word"difierential" should read "differential" Column 12, line 9, "arounnd"should read "around" Signed and sealed this 4th day of April 1972 (SEAL)Attest:

EDWARD M.FLETCHER,JR ROBERT GOTTSCHALK Attesting Officer Commissioner ofPatents

